/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.util.VersionInfo;
import org.apache.hadoop.hbase.zookeeper.ZKConfig;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Adds HBase configuration files to a Configuration
 */
@InterfaceAudience.Public
public class HBaseConfiguration extends Configuration {
    private static final Logger LOG = LoggerFactory.getLogger(HBaseConfiguration.class);

    /**
     * Instantiating HBaseConfiguration() is deprecated. Please use
     * HBaseConfiguration#create() to construct a plain Configuration
     *
     * @see #create()
     * @see <a href="https://issues.apache.org/jira/browse/HBASE-2036">HBASE-2036</a>
     * @deprecated since 0.90.0. Please use {@link #create()} instead.
     */
    @Deprecated
    public HBaseConfiguration() {
        //TODO:replace with private constructor, HBaseConfiguration should not extend Configuration
        super();
        addHbaseResources(this);
        LOG.warn("instantiating HBaseConfiguration() is deprecated. Please use" + " HBaseConfiguration#create() to construct a plain Configuration");
    }

    /**
     * Instantiating HBaseConfiguration() is deprecated. Please use
     * HBaseConfiguration#create(conf) to construct a plain Configuration
     *
     * @see #create(Configuration)
     * @see <a href="https://issues.apache.org/jira/browse/HBASE-2036">HBASE-2036</a>
     * @deprecated since 0.90.0. Please use {@link #create(Configuration)} instead.
     */
    @Deprecated
    public HBaseConfiguration(final Configuration c) {
        //TODO:replace with private constructor
        this();
        merge(this, c);
    }

    private static void checkDefaultsVersion(Configuration conf) {
        if(conf.getBoolean("hbase.defaults.for.version.skip", Boolean.FALSE))
            return;
        String defaultsVersion = conf.get("hbase.defaults.for.version");
        String thisVersion = VersionInfo.getVersion();
        if(!thisVersion.equals(defaultsVersion)) {
            throw new RuntimeException(
                    "hbase-default.xml file seems to be for an older version of HBase (" + defaultsVersion + "), this version is " + thisVersion);
        }
    }

    public static Configuration addHbaseResources(Configuration conf) {

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释： 加载配置文件
         */
        conf.addResource("hbase-default.xml");
        conf.addResource("hbase-site.xml");

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释： 检查 hbase-site.xml 的版本
         */
        checkDefaultsVersion(conf);
        return conf;
    }

    /**
     * Creates a Configuration with HBase resources
     *
     * @return a Configuration with HBase resources
     */
    public static Configuration create() {
        Configuration conf = new Configuration();
        // In case HBaseConfiguration is loaded from a different classloader than
        // Configuration, conf needs to be set with appropriate class loader to resolve
        // HBase resources.
        conf.setClassLoader(HBaseConfiguration.class.getClassLoader());

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释：
         */
        return addHbaseResources(conf);
    }

    /**
     * @param that Configuration to clone.
     * @return a Configuration created with the hbase-*.xml files plus
     * the given configuration.
     */
    public static Configuration create(final Configuration that) {
        Configuration conf = create();
        merge(conf, that);
        return conf;
    }

    /**
     * Merge two configurations.
     *
     * @param destConf the configuration that will be overwritten with items
     *                 from the srcConf
     * @param srcConf  the source configuration
     **/
    public static void merge(Configuration destConf, Configuration srcConf) {
        for(Map.Entry<String, String> e : srcConf) {
            destConf.set(e.getKey(), e.getValue());
        }
    }

    /**
     * Returns a subset of the configuration properties, matching the given key prefix.
     * The prefix is stripped from the return keys, ie. when calling with a prefix of "myprefix",
     * the entry "myprefix.key1 = value1" would be returned as "key1 = value1".  If an entry's
     * key matches the prefix exactly ("myprefix = value2"), it will <strong>not</strong> be
     * included in the results, since it would show up as an entry with an empty key.
     */
    public static Configuration subset(Configuration srcConf, String prefix) {
        Configuration newConf = new Configuration(false);
        for(Map.Entry<String, String> entry : srcConf) {
            if(entry.getKey().startsWith(prefix)) {
                String newKey = entry.getKey().substring(prefix.length());
                // avoid entries that would produce an empty key
                if(!newKey.isEmpty()) {
                    newConf.set(newKey, entry.getValue());
                }
            }
        }
        return newConf;
    }

    /**
     * Sets all the entries in the provided {@code Map<String, String>} as properties in the
     * given {@code Configuration}.  Each property will have the specified prefix prepended,
     * so that the configuration entries are keyed by {@code prefix + entry.getKey()}.
     */
    public static void setWithPrefix(Configuration conf, String prefix, Iterable<Map.Entry<String, String>> properties) {
        for(Map.Entry<String, String> entry : properties) {
            conf.set(prefix + entry.getKey(), entry.getValue());
        }
    }

    /**
     * @return whether to show HBase Configuration in servlet
     */
    public static boolean isShowConfInServlet() {
        boolean isShowConf = false;
        try {
            if(Class.forName("org.apache.hadoop.conf.ConfServlet") != null) {
                isShowConf = true;
            }
        } catch(LinkageError e) {
            // should we handle it more aggressively in addition to log the error?
            LOG.warn("Error thrown: ", e);
        } catch(ClassNotFoundException ce) {
            LOG.debug("ClassNotFound: ConfServlet");
            // ignore
        }
        return isShowConf;
    }

    /**
     * Get the value of the <code>name</code> property as an <code>int</code>, possibly referring to
     * the deprecated name of the configuration property. If no such property exists, the provided
     * default value is returned, or if the specified value is not a valid <code>int</code>, then an
     * error is thrown.
     *
     * @param name           property name.
     * @param deprecatedName a deprecatedName for the property to use if non-deprecated name is not
     *                       used
     * @param defaultValue   default value.
     * @return property value as an <code>int</code>, or <code>defaultValue</code>.
     * @throws NumberFormatException when the value is invalid
     * @deprecated it will be removed in 3.0.0. Use
     * {@link Configuration#addDeprecation(String, String)} instead.
     */
    @Deprecated
    public static int getInt(Configuration conf, String name, String deprecatedName, int defaultValue) {
        if(conf.get(deprecatedName) != null) {
            LOG.warn(String.format("Config option \"%s\" is deprecated. Instead, use \"%s\"", deprecatedName, name));
            return conf.getInt(deprecatedName, defaultValue);
        } else {
            return conf.getInt(name, defaultValue);
        }
    }

    /**
     * Get the password from the Configuration instance using the
     * getPassword method if it exists. If not, then fall back to the
     * general get method for configuration elements.
     *
     * @param conf    configuration instance for accessing the passwords
     * @param alias   the name of the password element
     * @param defPass the default password
     * @return String password or default password
     * @throws IOException
     */
    public static String getPassword(Configuration conf, String alias, String defPass) throws IOException {
        String passwd = null;
        try {
            Method m = Configuration.class.getMethod("getPassword", String.class);
            char[] p = (char[]) m.invoke(conf, alias);
            if(p != null) {
                LOG.debug(String.format("Config option \"%s\" was found through" + " the Configuration getPassword method.", alias));
                passwd = new String(p);
            } else {
                LOG.debug(String.format("Config option \"%s\" was not found. Using provided default value", alias));
                passwd = defPass;
            }
        } catch(NoSuchMethodException e) {
            // this is a version of Hadoop where the credential
            //provider API doesn't exist yet
            LOG.debug(String.format("Credential.getPassword method is not available." + " Falling back to configuration."));
            passwd = conf.get(alias, defPass);
        } catch(SecurityException e) {
            throw new IOException(e.getMessage(), e);
        } catch(IllegalAccessException e) {
            throw new IOException(e.getMessage(), e);
        } catch(IllegalArgumentException e) {
            throw new IOException(e.getMessage(), e);
        } catch(InvocationTargetException e) {
            throw new IOException(e.getMessage(), e);
        }
        return passwd;
    }

    /**
     * Generates a {@link Configuration} instance by applying the ZooKeeper cluster key
     * to the base Configuration.  Note that additional configuration properties may be needed
     * for a remote cluster, so it is preferable to use
     * {@link #createClusterConf(Configuration, String, String)}.
     *
     * @param baseConf   the base configuration to use, containing prefixed override properties
     * @param clusterKey the ZooKeeper quorum cluster key to apply, or {@code null} if none
     * @return the merged configuration with override properties and cluster key applied
     * @see #createClusterConf(Configuration, String, String)
     */
    public static Configuration createClusterConf(Configuration baseConf, String clusterKey) throws IOException {
        return createClusterConf(baseConf, clusterKey, null);
    }

    /**
     * Generates a {@link Configuration} instance by applying property overrides prefixed by
     * a cluster profile key to the base Configuration.  Override properties are extracted by
     * the {@link #subset(Configuration, String)} method, then the merged on top of the base
     * Configuration and returned.
     *
     * @param baseConf       the base configuration to use, containing prefixed override properties
     * @param clusterKey     the ZooKeeper quorum cluster key to apply, or {@code null} if none
     * @param overridePrefix the property key prefix to match for override properties,
     *                       or {@code null} if none
     * @return the merged configuration with override properties and cluster key applied
     */
    public static Configuration createClusterConf(Configuration baseConf, String clusterKey, String overridePrefix) throws IOException {
        Configuration clusterConf = HBaseConfiguration.create(baseConf);
        if(clusterKey != null && !clusterKey.isEmpty()) {
            applyClusterKeyToConf(clusterConf, clusterKey);
        }

        if(overridePrefix != null && !overridePrefix.isEmpty()) {
            Configuration clusterSubset = HBaseConfiguration.subset(clusterConf, overridePrefix);
            HBaseConfiguration.merge(clusterConf, clusterSubset);
        }
        return clusterConf;
    }

    /**
     * Apply the settings in the given key to the given configuration, this is
     * used to communicate with distant clusters
     *
     * @param conf configuration object to configure
     * @param key  string that contains the 3 required configuratins
     * @throws IOException
     */
    private static void applyClusterKeyToConf(Configuration conf, String key) throws IOException {
        ZKConfig.ZKClusterKey zkClusterKey = ZKConfig.transformClusterKey(key);
        conf.set(HConstants.ZOOKEEPER_QUORUM, zkClusterKey.getQuorumString());
        conf.setInt(HConstants.ZOOKEEPER_CLIENT_PORT, zkClusterKey.getClientPort());
        conf.set(HConstants.ZOOKEEPER_ZNODE_PARENT, zkClusterKey.getZnodeParent());
    }

    /**
     * For debugging.  Dump configurations to system output as xml format.
     * Master and RS configurations can also be dumped using
     * http services. e.g. "curl http://master:16010/dump"
     */
    public static void main(String[] args) throws Exception {
        HBaseConfiguration.create().writeXml(System.out);
    }
}
